1. Field of the Invention
The present invention relates to a blade sharpener that sharpens blades such as kitchen knives and table knives with an abrasive wheel and more particularly to a manual blade sharpener having an abrasive wheel therein.
2. Background Art
Japanese Patent Application Laid-Open (Kokai) No. S62-181860 discloses a table knife sharpener that is comprised of a main frame casing, a adhesive wheel rotatably installed in this main frame casing and equipped with grinding surfaces that are of a truncated cone shape and forming an angle to each other, a guide part that guides the blade so that the blade being sharpened is pressed against both grinding surfaces, and a liquid vessel installed in the main frame casing so as to surround the bottom part of the abrasive wheel.
In this device, two sides of the blade of a knife is pressed against the two sides of the grindstone and the knife is moved back and forth at a bias relative to the axial direction of the abrasive wheel that has truncated conical grinding surfaces to sharpen both sides of the blade. This device has problems, however. During sharpening by the back and forth movements of the blade, frictional heat is generated, thus dulling the blade. Grinding dust from the blade would clog the pores of the abrasive wheel. Though the liquid vessel that contains liquid for cooling and cleaning the blade during the sharpening is provided, the problems of the frictional heat and clogging are not sufficiently solved. Furthermore, since the abrasive wheel is fixedly provided in the main frame casing, it is difficult to wash and clean the abrasive wheel.
Japanese Utility Model Registration No 3007312 discloses a blade sharpener that is to solve the problems above. This blade sharpener includes a main frame casing having a grip and a grinding chamber, a rotary shaft rotatably installed across the grinding chamber and arranged at a bias to the direction of the length of the main frame casing, an abrasive wheel that is installed in the center of the rotary shaft and has grinding surfaces which are truncated cones and form an angle to each other, a guide part that guides the blade so that the blade being sharpened is pressed against the two grinding surfaces, and a liquid vessel installed in the grinding chamber so that the liquid therein for cooling the abrasive wheel can surround the bottom part of the abrasive wheel. Also, Japanese Utility Model Registration No 3010973 discloses a sharpener for a single-blade knife in which an abrasive element is comprised of a pair of roller bodies having conical surfaces and one of the conical surfaces is a grinding surface and the other conical surface is a smooth, hard, non-grinding surface.
In these blade sharpeners described above, the side of a blade is, while being pressed against the grinding surface, sharpened by moving the blade back and forth along the guide part while it is being pressed against the conical surface of an abrasive wheel. Accordingly, sharpened conditions of blades can differ depending on how (in terms of pressing loads, pressing angles, etc.) the blade is pressed against the abrasive wheel. Pressing the blade too firmly will create defects in the cutting edge and can leave it to be able to cut less than before. In addition, blades with serrated cutting edges and fine ceramic blades cannot be sharpened very well even with use of a diamond abrasive wheel for the grinding surface.
Japanese Utility Model Registration No 3128435 discloses a blade sharpener that is to overcome the problems described above, and in this sharpener a rotary shaft that has an abrasive wheel is supported at both end thereof by a pair of vertically installed springs so that the blade can be evenly pressed against the abrasive wheel and evenly ground by the conical surfaces of the abrasive wheel.